Flat panel display embedding optical imaging sensor

ABSTRACT

Discussed is a flat panel display device embedding an optical imaging sensor such as a fingerprint image sensor. The device includes: a display panel including a display area and a non-display area, and having a top surface; and a directional optical unit attached to the top surface of the display panel, the directional optical unit having a length along a length axis of the display panel, a width along a width axis of the display panel and a thickness along a thickness axis of the display panel, wherein the directional optical unit provides a sensing light to the display area, and wherein the sensing light is collimated and directionized along a predetermined direction of the directional optical unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korea Patent Application No.10-2016-0082707 filed on Jun. 30, 2016, the disclosure of which isincorporated herein by reference for all purposes as if fully set forthherein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a flat panel display embedding anoptical imaging sensor such as a fingerprint image sensor. Inparticular, the present disclosure relates to a flat panel displayembedding an optical imaging sensor including an ultra thin substrateproviding the directional lights and an optical imaging sensor.

Description of the Related Art

Various computer based systems including the notebook computer, thetablet personal computer (or, PC), the smart phone, the personal digitalassistants, the automated teller machines and/or the search informationsystem have been developed. As these devices use and store the variouspersonal information as well as the business information and the tradesecrets, it is desirable to strengthen the securities for preventingthese important data being leaked.

To do so, one method has been suggested for strengthening the securityusing an image sensor recognizing the authorized user's biologicalinformation. For example, the fingerprint sensor is generally used forenhancing the security when registering and authenticating is performed.The fingerprint sensor is for sensing the fingerprint of a user. Thefingerprint sensor may be categorized into the optical fingerprintsensor and the capacitive fingerprint sensor.

The optical fingerprint sensor uses a light source such as a lightemitting diode (or LED) to irradiate lights and detects the lightsreflected by the ridge of the fingerprint using a CMOS (or,complementary metal oxide semiconductor) image sensor. As the opticalfingerprint sensor may scan the fingerprint using the LED lights, it isrequired that the sensor is equipped with an additional device forperforming the scan process. There is a limitation to increasing thesize of the object for scanning the image. Therefore, there arelimitations for applying the optical fingerprint sensor to variousapplications such as combining with the display devices.

For conventional optical fingerprint sensors, known are a Korean patent10-060817 registered on Jun. 26, 2006 of which title is “A displayapparatus having fingerprint identification sensor” and a Korean patentapplication 10-2016-0043216 published on Apr. 21, 2016 of which title is“Display device including fingerprinting device”.

The above mentioned optical fingerprint sensor is configured to use thedisplay area as the touch area for inputting the user's selection andthe sense area for sensing the fingerprint. However, this opticalfingerprint sensor uses the diffused (or diverged) lights having verylow directivity. Therefore, there is a limitation to recognize the exactfingerprint pattern. When using the collimated lights such as theinfrared laser having high directivity, it is very hard to generate thesensing lights to cover the wider area. Therefore, the fingerprintsensing area is restricted in a small area. In order to radiate thecollimated lights over the wider scan area, specific scanning structureis required, so that this system is not suitable for portable orpersonal display apparatus.

Therefore, for portable devices embedding the fingerprint sensor, thecapacitive fingerprint sensor is mainly used. However, the capacitivefingerprint sensor also has many problems.

The capacitive fingerprint sensor is configured to detect the differenceof the electricity between the ridge and the valley of the fingerprintcontacting on the fingerprint sensor. For conventional capacitivefingerprint sensors, known is a US patent application 2013/0307818published on Nov. 21, 2013 of which title is “Capacitive SensorPackaging”.

The above mentioned capacitive fingerprint sensor is configured as anassembly type embedding with a specific push button. It comprises acapacitive plate and a silicon wafer having a circuit for detecting thecapacitive storage between the ridge and valley of the fingerprint.Generally, as the sizes of the ridge and valley of the fingerprint arevery tiny, about 300˜500 μm (micrometer), the capacitive fingerprintsensor needs a high resolution sensor array and an integrated chip (orIC) for processing the fingerprint detection. To do so, the siliconwafer is configured to include the sensor array and the IC on onesubstrate.

However, when the high resolution sensor array and the IC are formed onthe same silicon wafer, the assembly structure is required for joiningthe push button with the fingerprint sensor. Therefore, the structurewould be very complex and further the non-display area (or bezel area)may be increased. In some instances, the push button (i.e., the home keyof the smart phone) would be overlapped with the fingerprint sensor, sothat the thickness of the whole device would be thick. Further, thesensing area for the fingerprint would be dependent on the size of thepush button.

To solve the above mentioned problems and limitations, some technologieshave been suggested in which the touch sensor area is used as forsensing the fingerprint. For example, known are U.S. Pat. No. 8,564,314issued on Oct. 22, 2013 of which title is “Capacitive touch sensor foridentifying a fingerprint”, and a Korean patent 10-1432988 registered onAug. 18, 2014 of which title is “A capacitive touch screen forintegrated of fingerprint recognition”.

In general instances of the personal portable devices such as the smartphones, an additional transparent film is attached for protecting thedisplay glass panel. When the above mentioned technologies are appliedto the personal portable devices, as attaching the protective filmthereon, the performance for sensing or recognizing the fingerprintexactly would be remarkably degraded. In general, even though theprotective film is attached, the touch function may be properlyoperated. However, the detection ability for the difference of thecapacitive storage amount for sensing the fingerprint may bedeteriorated by the protective film even though its thickness is verythin.

For a display embedding the capacitive fingerprint sensor, generally aprotective film or a hardening glass may be further attached on thecover glass of the display. In that instance, the recognition abilitymay be deteriorated. That is, the total thickness of the cover glass mayaffect the sensitivity of the capacitive fingerprint sensor. In theinterim, the diffused lights used in the sensing light source may affectthe sensitivity of the optical fingerprint sensor. When using thecollimated lights for enhancing the sensitivity of the opticalfingerprint sensor, the bulky and/or complex optical devices arerequired so that it is very hard to apply the technique to a display fora personal mobile device.

SUMMARY OF THE INVENTION

In order to overcome the above mentioned drawbacks, a purpose of thepresent disclosure is to provide a flat panel display embedding an ultrathin optical image sensor (or an optical image recognition apparatus).Another purpose of the present disclosure is to provide a flat paneldisplay having an optical image sensor in which most or all of a surfaceof the display panel may be used for the sensing area. Still anotherpurpose of the present disclosure is to provide a flat panel displayembedding an optical image sensor in which a directional light is usedas a sensing light covering a large surface area. Yet another purpose ofthe present disclosure is to provide a flat panel display embedding anultra thin and large area optical image sensor of which resolution andsensitivity are very high and/or superior.

In order to accomplish one or more of the above purposes, the presentdisclosure provides a flat panel display device embedding an imagesensor, the device including: a display panel including a display areaand a non-display area, the display panel having a top surface; and adirectional optical unit attached to the top surface of the displaypanel, the directional optical unit having a length along a length axisof the display panel, a width along a width axis of the display paneland a thickness along a thickness axis of the display panel, wherein thedirectional optical unit provides a sensing light to the display area,and wherein the sensing light is collimated and directionized along apredetermined direction of the directional optical unit.

In one embodiment, the directional optical unit includes: a light guideoptical plate having a size corresponding to the length and the width ofthe directional optical unit; a light radiating film corresponding tothe display area, the light radiating film positioned under the lightguide optical plate; a light incident film positioned under the lightguide optical plate and disposed outside of the display area adjacent toa lateral side of the light radiating film; a first low refractive layerdisposed under the light radiating film and the light incident film, thefirst low refractive layer attached on the top surface of the displaypanel, and having a first refractive index that is lower than that ofthe light guide optical plate and that of the light radiating film; asecond low refractive layer disposed on the light guide optical plate,and having a second refractive index lower than that of the light guideoptical plate; and a light source positioned under the light incidentfilm.

In one embodiment, the light source provides an incident light to anincident point on a surface of the light incident film; the lightincident film includes a first holographic pattern that converts theincident light to a propagating light having an incident anglesatisfying an internal total reflection condition of the light guideoptical plate, and that transmits the propagating light into the lightguide optical plate; and the light radiating film includes a secondholographic pattern that converts a portion of the propagating lightinto the sensing light, the sensing light having a reflection angle thatsatisfies a total reflection condition at a top surface of the secondlow refractive layer and that satisfies a transmitting condition throughthe first low refractive layer and the display panel.

In one embodiment, the propagating light has an expanding angle on ahorizontal plane including the length axis and the width axis of thedisplay panel, and the propagating light maintains a collimated state ona vertical plane including the length axis and the thickness axis of thedisplay panel; the incident angle is larger than a first internal totalreflection critical angle at a first interface between the lightradiating film and the first low refractive layer, and larger than asecond internal total reflection critical angle at a second interfacebetween the light guide optical plate and the second low refractivelayer; and the reflection angle is larger than a third total reflectioncritical angle at a third interface between the second low refractivelayer and an air layer, and smaller than a fourth total reflectioncritical angle at a fourth interface between the first low refractivelayer and the display panel.

In one embodiment, the expanding angle is equal to or greater than aninner angle between a first line and a second line, the first line is astraight line between the incident point and a first end of a side ofthe light guide optical plate opposite to the light incident film, andthe second line is a straight line between the incident point and asecond end of the side of the light guide optical plate opposite to thelight incident film.

In one embodiment, the directional optical unit further includes: ahorizontal collimating film disposed under the light guide optical platebetween the light incident film and the light radiating film, thehorizontal collimating film having a width corresponding to the width ofthe directional optical unit, wherein the expanding angle is equal to orgreater than an inner angle between a first line and a second line, thefirst line is a straight line between the incident point and a first endof a side of the horizontal collimating film opposite to the lightincident film, and the second line is a straight line between theincident point and a second end of the side of the horizontalcollimating film opposite to the light incident film, and wherein thehorizontal collimating film includes a third holographic pattern thathorizontally collimates the propagating light having the expanding angleon the horizontal plane corresponding to the width of the directionaloptical unit.

In one embodiment, the directional optical unit further includes: ahorizontal collimating film disposed at an opposite side of the lightguide optical plate facing the light incident film in the non-displayarea, wherein the light incident film includes a third holographicpattern that converts the incident light to a total reflecting lighthaving a total reflection angle different from the incident angle, andthat transmits the total reflecting light into the light guide opticalplate, wherein the expanding angle is equal to or greater than an innerangle between a first line and a second line, the first line is astraight line between the incident point and a first end of a side ofthe horizontal collimating film, and the second line is a straight linebetween the incident point and a second end of the side of thehorizontal collimating film, the second end being opposite to the firstend, wherein the horizontal collimating film includes a thirdholographic pattern that horizontally collimates the propagating lighthaving the expanding angle on the horizontal plane corresponding to thewidth, and that converts the total reflecting light to the propagatinglight and transmits the propagating light to the light incident film,and wherein the second holographic pattern of the light radiating filmis for transmitting the total reflecting light therethrough.

In one embodiment, the light guide optical plate is a cover plate of thedisplay panel.

In one embodiment, the flat panel display embedding an image sensorfurther includes: a cover plate attached on the first low refractivelayer.

The present disclosure provides a flat panel display embedding anoptical image sensor that has a high resolution recognizing ability orsensitivity by providing the directionized lights (or ‘oriented’) as thesensing lights. Comparing with the diffused lights used in theconventional art for the fingerprint sensor, because the directionizedlights according to the present disclosure are used for sensing theimage without any loss of lights, the present disclosure has the meritsof the higher resolution and the superior sensitivity. The presentdisclosure provides a flat panel display embedding a large area opticalimage sensor in which a collimated infrared laser beam is expanded overa large area corresponding to the display panel for sensing lights usinga holography technology. The present disclosure provides a flat paneldisplay having an ultra thin optical image sensor in which a directionlight is provided on the display surface within a thin thickness.Further, according to the present disclosure, the protective substratedisposed on the topmost surface is used as the cover substrate of thedirection optical substrate. Using a holographic film, the collimatedlight is provided as covering the large area corresponding to thedisplay surface so that the present disclosure provides an ultra thindirection optical substrate. When joining the optical image sensor tothe display device, the whole thickness of the display device is notthicker. As the image sensing area may be set freely within the displayarea of the display device, the flat panel display embedding an opticalimage sensor according to the present disclosure may be applied tovarious applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain the principles of thedisclosure.

In the drawings:

FIG. 1 is a drawing illustrating a structure of a directional opticalsubstrate applied for a flat panel display embedding an optical imagesensor according to a first embodiment of the present disclosure.

FIG. 2 is a cross sectional view illustrating light paths inside of thedirectional optical substrate shown in FIG. 1.

FIG. 3 is a drawing illustrating a structure of a flat panel displayembedding an optical image sensor including a directional optical unitand an optical sensor, according to the first embodiment of the presentdisclosure.

FIG. 4 is a drawing illustrating a structure of a flat panel displayembedding an optical image sensor including a directional optical unitand an optical sensor, according to a second embodiment of the presentdisclosure.

FIG. 5 is a drawing illustrating a structure of a flat panel displayembedding an optical image sensor including a directional optical unitand an optical sensor, according to a third embodiment of the presentdisclosure.

FIGS. 6A and 6B are cross sectional views illustrating light pathsinside of the directional optical substrate according to the thirdembodiment.

FIGS. 7A and 7B are cross sectional views illustrating how the lightsare provided in view of the relationship of the cover plate and thelight source in the direction optical unit according to a fourthembodiment of the present disclosure.

FIG. 8 is a cross sectional view illustrating profiles of the lightsinside of the directional optical unit according to a fifth embodimentof the present disclosure.

FIG. 9 is a cross sectional view illustrating profiles of the lightsinside of the directional optical unit according to a sixth embodimentof the present disclosure.

FIG. 10 is a cross sectional view illustrating a structure of a liquidcrystal display embedding an optical image sensor including adirectional optical unit and an optical sensor according to a firstapplication example, in accordance with embodiments of the presentdisclosure.

FIG. 11 is a cross sectional view illustrating a structure of an organiclight emitting diode display embedding an optical image sensor includinga directional optical unit and an optical sensor according to a secondapplication example, in accordance with embodiments of the presentdisclosure.

FIG. 12 is a cross sectional view illustrating a structure of an organiclight emitting diode display embedding an optical image sensor includinga directional optical unit and an optical sensor according to a thirdapplication example, in accordance with embodiments of the presentdisclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to the attached figures, one or more example embodiments ofthe present disclosure will be described. Like reference numeralsdesignate like elements throughout the detailed description. However,the present disclosure is not restricted by these embodiments but can beapplied to various changes or modifications without changing thetechnical spirit of the disclosure. In the following embodiments, thenames of the elements are selected by considering the ease forexplanation so that they may be different from actual names.

<First Embodiment>

Hereinafter, referring to FIGS. 1 and 2, a first embodiment of thepresent disclosure will be described. FIG. 1 is a drawing illustrating astructure of a directional optical substrate applied for a flat paneldisplay embedding an optical image sensor according to the firstembodiment of the present disclosure. In FIG. 1, the upper drawing (a)is a side view on the XZ plane and the lower drawing (b) is a plane viewon the XY plane.

Referring to FIG. 1, a directional optical unit according to the firstembodiment comprises a directional optical substrate SLS and a lightsource LS. The directional optical substrate SLS includes a cover plateCP, a light radiating film VHOE, a light incident film CHOE, a first lowrefractive layer LR1 and a second low refractive layer LR2. The coverplate CP may have a rectangular plate shape having a length, a width anda thickness. In FIG. 1, the length is along the X-axis, the width isalong the Y-axis and the thickness is along the Z-axis.

The directional optical unit is an optical device for providing thecollimated light expanded covering a large area corresponding to asurface of the display. Therefore, it is preferable that the lightsource LS provides a collimated light.

On the bottom surface of the cover plate CP, the light radiating filmVHOE and the light incident film CHOE are attached. The light radiatingfilm VHOE is an optical element for providing the radiating light orlights 300. It is preferable that the light radiating film VHOE isdisposed as corresponding to the area for detecting and/or sensing theimage.

The light incident film CHOE is an optical element for converting thecollimated light provided from the light source into the lights expandedover the area of the cover plate CP. It is preferable that the lightincident film CHOE is disposed outside of and adjacent to the lightradiating film VHOE. Specifically, the light incident film CHOE isdisposed as facing the light source LS.

It is preferable that the light radiating film VHOE and the lightincident film CHOE may be disposed on the same plane level. Consideringthe manufacturing process, it is further preferable that the lightradiating film VHOE and the light incident film CHOE are formed as beingseparated from each other, on a same film. The light radiating film VHOEand the light incident film CHOE may be optical elements having theholographic patterns. In this instance, after disposing the master filmfor the light radiating film VHOE and the master film for the lightincident film CHOE to be close to each other, these two holographicpatterns may be copied on one holographic recording film, at the sametime.

Under the bottom surface of the light radiating film VHOE and the lightincident film CHOE, a first low refractive layer LR1 is disposed. It ispreferable that the first low refractive layer LR1 has the refractiveindex lower than that of the cover plate CP and the light radiating filmVHOE. For example, the cover plate CP may be formed of a transparentreinforced glass having a refractive index of 1.5. The light radiatingfilm VHOE and the light incident film CHOE may be the transparentholographic recording film and may have a refractive index that is thesame as or slightly larger than that of the cover plated CP. Here, weuse the instance that the refractive index of the light radiating filmVHOE and the light incident film CHOE are the same as that of the coverplate CP. It is preferable that the refractive index of the first lowrefractive layer LR1 is equal to or smaller than the refractive index ofthe scanning objects.

Further, the second low refractive layer LR2 is stacked on the uppersurface of the cover plate CP. It is preferable that the first lowrefractive layer LR1 has the refractive index lower than the cover plateCP and/or the light radiating film VHOE. In addition, it is preferablethat the first low refractive layer LR1 and the second low refractivelayer LR2 have the same refractive index. For example, when applied tothe fingerprint sensor, the first low refractive layer LR1 and thesecond low refractive layer LR2 may have a refractive index of 1.4,which is similar with the refractive index of human skin, 1.39.

Accordingly, the cover plate CP and the light radiating film VHOE havingthe refractive index of 1.5 are inserted between the first lowrefractive layer LR1 and the second low refractive layer LR2. In otherwords, the stack structure is such that the lower refractive layers aredisposed on the upper surface and on the lower surface of the higherrefractive layer. This structure satisfies the condition that the lightscan propagate within the higher refractive layer as the lights aretotally reflected.

At the space under the light incident film CHOE, the light source LS isdisposed as facing the light incident film CHOE. It is preferable thatthe light source LS provides a highly collimated light such as a LASERbeam. Specifically, when applied to the system in which the fingerprintsensor is embedded into a portable display, it is preferable that thelight source LS provides the infrared laser beam which cannot berecognized by the human eyes.

The collimated light from the light source LS, as an incident light 100,having a predetermined cross sectional area is provided to a lightincident point IP defined on the light incident film CHOE. It ispreferable that the incident light 100 enters onto the normal directionwith respect to the surface of the incident point IP. However,embodiments provided by the present disclosure are not restricted assuch, For example, in one or more embodiments, the incident light 100may enter onto the incident point IP with an inclined angle with respectto the normal direction.

The light incident film CHOE converts the incident light 100 into apropagating light 200 having an incident angle and sends it into thecover plate CP. Here, it is preferable that the incident angle is largerthan the internal total reflection critical angle of the cover plate CP.Accordingly, in repeating the total reflection, the propagating light200 propagates inside of the cover plate CP along the X-axis, the lengthdirection of the cover plate CP.

The light radiating film VHOE converts some amount of the propagatinglight 200 into the radiating light 300 and refracts the radiating light300 to the upper surface of the cover plate CP. Other portions of thepropagating light 200 would continuously be propagating inside of thecover plate CP. At the upper surface of the cover plate CP, theradiating light 300 goes into the second low refractive layer LR2.However, at the upper surface of the second low refractive layer LR2,the radiating light 300 is totally reflected, because the upper surfaceof the second low refractive layer LR2 contacts the air layer having therefractive index of 1.0. Further, it would pass through the first lowrefractive layer LR1 at the bottom surface of the cover plate CP. As thefirst low refractive layer LR1 contacts the upper substrate of thedisplay panel DP having the refractive index larger than the first lowrefractive layer LR1, the radiating light 300 goes out of thedirectional optical substrate SLS. In other words, the radiating light300 totally reflected at the upper surface of the second low refractivelayer LR2 would be a sensing light 400 as passing through the bottomsurface of the cover plate CP.

As the propagating light 200 goes from the light incident film CHOE tothe opposite side, a predetermined portion of the propagating light 200is extracted as the radiating lights 300 by the light radiating filmVHOE. The amount (or ‘brightness’ or ‘luminance’) of the radiating light300 is determined by the light extraction efficiency of the lightradiating film VHOE. For example, when the light extraction efficiencyof the light radiating film VHOE is 3%, then 3% of the initial lightamount of the propagating light 200 would be extracted at the firstradiating point where the propagating light 200 firstly hits the lightradiating film VHOE. Then, the 97% of the propagating light 200 would betotally reflected at the first radiating point and goes on continuously.After that, at the second radiating point, 3% of the 97%, i.e., 2.91% ofthe initial amount of the propagating light 200 would be extracted asthe radiating light 300.

Repeating this operation, a plurality of radiating lights 300 would beextracted from the first side where the light incident film CHOE isdisposed to the opposite side. When the light radiating film VHOE hasthe light extraction efficiency the same over all areas, the amount ofthe propagating light 200 is gradually lowered as propagating from thefirst side to the opposite side. In order to get an evenly distributedamount of the lights over the whole area of the light radiating area, itis preferable that the light extraction efficiency of the lightradiating film VHOE is exponentially increased from the first side tothe opposite side.

In observing the propagating light 200 on the XZ plane (or, ‘verticalplane’) having the length axis and the thickness axis, the collimatedcondition of the incident light 100 is maintained. On the contrary, onthe XY plane (or, ‘horizontal plane’) having the length axis and thewidth axis, it is preferable that the propagating light 200 is adiverged (or, expanded) light having an expanding angle, ϕ. The reasonfor expanding the propagating light 200 is that the image sensing areais set as covering most of the area of the cover plate CP. For example,it is preferable that the light radiating film VHOE has an areacorresponding to the whole area of the light going-out part LOT.Further, it is preferable that the expanding angle ϕ is the inside anglebetween two lines, one line is connecting the incident point IP and oneend point P1 of the opposite side of the cover plate CP, and the otherline is connecting the incident point IP and another end point P2 of theopposite side of the cover plate CP.

The area where the light incident film CHOE is disposed would be definedas a light entering part LIN. The area where the light radiating filmVHOE is disposed would be defined as a light going-out part LOT. Thelight going-out part LOT would be the light propagating part where thelight is going through. In FIG. 1, the light incident film CHOE coversthe whole area of the light entering part LIN. However, it is enoughthat the light incident film CHOE has a size slightly larger than thesize of the light incident point IP.

For example, the cross sectional size of the collimated light generatedfrom the light source LS may have the right circle shape of which aradius is 0.5 mm. The light incident film CHOE would have the lengthcorresponding to the width of the cover plate CP and the width of 3 mm˜5mm. The light incident film CHOE may be disposed as covering the widthof the cover plate CP.

Hereinafter, referring to FIG. 2, explanation will be given of how thecollimated infrared light provided from the light source is convertedinto a directional infrared light used for image sensing inside of thedirectional optical substrate SLS. FIG. 2 is a cross sectional viewillustrating light paths inside of the directional optical substrateaccording to the FIG. 1.

The incident light 100 provided from the light source LS enters onto thenormal direction with respect to the surface of the incident point IP ofthe light incident film CHOE. The light incident film CHOE converts theincident light 100 into a propagating light 200 refracted as having anincident angle θ to the normal direction with respect to the surface ofthe incident point IP. Then, the light incident film CHOE provides thepropagating light 200 to the inside space (or ‘the media’) of the coverplate CP.

It is preferable that the incident angle θ of the propagating light 200is larger than the total reflection critical angle T_(VHOE_LR1) at theinterface between the light radiating film VHOE and the first lowrefractive layer LR1. Further, it is preferable that the incident angleθ of the propagating light 200 is larger than the total reflectioncritical angle T_(CP_LR2) at the interface between the cover plate CPand the second low refractive layer LR2. For example, when therefraction index of the cover plate CP and the light radiating film VHOEis 1.5, and the refraction index of the first low refractive layer LR1and the second low refractive layer LR2 is 1.4, it is preferable thatthe total reflection critical angle T_(VHOE_LR1) at the interfacebetween the light radiating film VHOE and the first low refractive layerLR1 and the total reflection critical angle T_(CP_LR2) at the interfacebetween the cover plate CP and the second low refractive layer LR2 aregreater than 69° (degrees). Therefore, it is preferable that theincident angle θ is larger than 69°. For example, the incident angle θmay be in the range of 70° to 75°, inclusive.

The light radiating film VHOE converts a predetermined amount of thepropagating light 200 into a radiating light 300 having a reflectionangle α and sends the radiating light 300 back into the inside space ofthe cover plate CP. The radiating light 300 is for detecting an image ofan object when the object is contacting on the upper surface of thesecond low refractive layer LR2. When there is no object on the outersurface of the second low refractive layer LR2, the radiating light 300is totally reflected at the upper surface of the second low refractivelayer LR2 and then is provided to the photo sensor (or, optical sensor)disposed at the outside of the bottom surface of the directional opticalsubstrate SLS. That is, after being totally reflected at the uppersurface of the second low refractive layer LR2, the radiating light 300goes out of the directional optical substrate SLS through the bottomsurface of the cover plate CP. All of the sensing lights 400 have thesame reflecting angle so that the sensing lights 400 are oriented (or‘directionized’) to a predetermined direction.

By detecting the sensing light 400 radiated out of the first lowrefractive layer LR1 disposed under the bottom surface of thedirectional optical substrate SLS, the images of the object contacted onthe upper surface of the second low refractive layer LR2 may berecognized. Hereinafter, explanation will be given about the imagesensing device being applied to the directional optical unit as shown inFIG. 1. Specifically, we focus on a flat panel display embedding afingerprint recognizing sensor. FIG. 3 is a drawing illustrating astructure of a flat panel display embedding an optical image sensorincluding a directional optical unit and an optical sensor, according tothe first embodiment of the present disclosure.

Referring to FIG. 3, with (a) being a side view and (b) being aperspective view, a flat panel display embedding an optical image sensoraccording to the first embodiment of the present disclosure comprises adisplay panel DP, a directional optical substrate SLS and a light sourceLS. The display panel DP includes a display area AA and a non-displayarea NA. The display area AA may be disposed at the middle portions ofthe display panel DP. The non-display area NA may be surrounding thedisplay area AA. The display area AA may have a plurality of the displayelements for representing the video images shown on the display panelDP. The non-display area NA may have a plurality of the driving elementsfor operating the display elements arrayed in the display area AA.

In detail, a plurality of pixel areas for representing the video imagesmay be arrayed in a matrix manner in the display area AA. At least oneof the pixel areas, one photo sensor may be included for detecting theimage of the object. In some instances, one photo sensor may be disposedat one group of the pixel areas. For example, one photo sensor may bedisposed at every pixel group including 2×2, 3×3 or 4×4 pixels.

The directional optical substrate SLS may be a thin plate having apredetermined length, width and thickness. It is preferable that thelength and width of the directional optical substrate SLS has a sizecorresponding to the size of the display panel DP. Specifically, it ispreferable that the directional optical substrate SLS has a sizeslightly larger than that of the display panel DP. At least, it ispreferable that the directional optical substrate SLS has an extended(or expanded) area over one side of the display panel DP. At theextended side area over the display panel DP, the light source LS may bedisposed.

The directional optical substrate SLS may be joined with the displaypanel DP as it is attached on the upper surface of the display panel DP.The directional optical substrate SLS includes a cover plate CP, a lightincident film CHOE, a light radiating film VHOE, a first low refractivelayer LR1 and a second low reflective layer LR2, as mentioned above. Itis preferable that the first low refractive layer LR1 is attached on theupper surface of the display panel DP as facing each other. Here, theupper surface of the display panel DP is the front face providing thevideo images from the display panel DP. That is, the user observes thevideo image as seeing the upper surface of the display panel DP.

The directional optical substrate SLS, as mentioned above, may providethe image sensing light 400 to the bottom surface which faces the uppersurface of the display panel DP. Therefore, the photo sensor disposed inthe display panel DP located under the directional optical substrate SLSmay detect the image sensing light 400. Accordingly, the images of theobject (for example, the shape of ridges of the fingerprint) contactingon the upper surface of the directional optical substrate SLS may berecognized.

In detail, the radiating light 300 generated by the light radiating filmVHOE of the directional optical substrate SLS would reach to the uppersurface of the second low refractive layer LR2. When an object IM isdisposed on the second low refractive layer LR2, the radiating light 300that hits the areas where the object IM is not contacting the uppersurface of the cover plate CP is totally reflected and provided to thedisplay panel DP as the sensing light 400. On the contrary, theradiating light 300 that hits the area where the object IM is contactingthe upper surface of the cover plate CP (e.g., at ridge R) is refractedand goes out through the cover plate CP. At the point where the objectIM having a refraction index larger than that of second low refractivelayer LR2 is contacting the upper surface of the second low refractivelayer LR2, the radiating light 300 is not totally reflected but it isrefracted into the object IM. That is, at the area where the object IMis contacting, the radiating light 300 would be an absorbed light 500 sothat it is not provided to the photo sensor of the display panel DP.

Accordingly, the photo sensor of the display panel DP detects only thesensing lights 400 except the absorbed lights 500 among the radiatinglights 300. Detecting the reflection patterns of the sensing lights 400reflected at the top surface of the second low refractive layer LR2, thephoto sensors of the display panel DP reproduces the patterns or imagesof the object IM.

When applying the directional optical unit to the fingerprint sensor,the object IM would be the finger of the human. The ridge R of thefingerprint is contacting on the top surface of the cover plate CP butthe valley V of the fingerprint is not contacting with the top surfaceof the cover plate CP. The radiating lights 300 that hit the uppersurface of the second low refractive layer LR2 at the valley V aretotally reflected to be the sensing lights 400. In the interim, theradiating lights 300 that hit the upper surface of the second lowrefractive layer LR2 at the ridge R are refracted so that they would bethe absorbed lights 500 going out of the cover plate CP.

Further referring to the lower drawing of FIG. 3, explanation will begiven about the process of the image sensing on the XY plane. Theincident light 100 may include a collimated infrared light having apredetermined cross sectional area. The light source LS may be aninfrared LASER diode (or ‘IR LD’).

The incident light 100 would be converted to a propagating light 200 bythe light incident film CHOE. Here, the propagating light 200 would beexpanded as having an expanding angle ϕ on the XY plane including thelength axis on the X axis and the width axis on the Y axis. In theinterim, on the XZ plane including the length axis on the X axis and thethickness axis on the Z axis, the initial collimated condition would bemaintained.

Here, it is preferable that the expanding angle ϕ is equal to orslightly larger than the inside angle of two lines connecting from thelight incident point IP to the two end points (i.e., the two corners atthe opposite side) of the cover plate CP facing the light incident filmCHOE, respectively. In this instance, the propagating light 200 may beexpanded as having a triangular shape. Accordingly, the radiating lights300 may cover the same area covered as the propagating light 200 isexpanded. That is, the image sensing area would be defined inside of thetriangular shape. When applied to the fingerprint sensor, thefingerprint sensing area SA may be defined as the circle area hatched inFIG. 3.

When setting the sensing area SA on the center portion or onupside-shifted portion facing the light incident film CHOE, it ispreferable that the amount (or luminance or brightness) of the radiatinglights 300 has a maximum value at the area corresponding to the sensingarea SA. To do so, the light radiating film VHOE may be designed ashaving varying light extraction efficiency according to the functionalrelationship with the position (i.e., the light radiating film VHOE mayhave a light extraction efficiency that varies as a function of positionalong the light radiating film VHOE), to have the maximum value at thearea corresponding to the sensing area SA and to have a minimum or zerovalue at the other areas (i.e., at areas outside of the sensing areaSA).

<Second Embodiment>

Hereinafter, referring to FIG. 4, explanation will be given about thesecond embodiment of the present disclosure. FIG. 4 is a drawingillustrating a structure of a flat panel display embedding an opticalimage sensor including a directional optical unit and an optical sensor,according to the second embodiment of the present disclosure, with (a)being a side view and (b) being a perspective view.

In the second embodiment of the present disclosure, explanation will begiven about the instance in which the image sensing area SA is muchwider than the first embodiment. Specifically, most of the display areaAA may be defined as the image sensing area SA.

The flat panel display embedding the optical image sensor is basicallysimilar with the first embodiment. The different point is that the flatpanel display embedding the optical image sensor according to the secondembodiment further comprises a horizontal collimating film PHOE forcollimating the expanded propagating light 200 on the XY plane as havingthe collimated width corresponding to the width of the cover plate CP.

The horizontal collimating film PHOE is disposed as being spaced apartfrom the light incident film CHOE to the direction of the propagatinglight 200 along the X axis, and as covering the width of the cover plateCP. Here, the distance from the light incident film CHOE to thehorizontal collimating film PHOE may be decided variously according tothe desired position and/or shape of the sensing area SA. For example,when the image sensing area SA is covering the ⅔ portions of the coverplate CP, the horizontal collimating film PHOE may be placed at the ⅓length position of the cover plate CP from the light incident film CHOE.

In that instance, the expanding angle ϕ may be corresponding to theinside angle between two lines connecting the light incident point IP toeach of both length end points of the horizontal collimating film PHOE,respectively. The propagating light 200 having the expanding angle ϕwould be converted into a horizontally collimated propagating light 201by the horizontal collimating film PHOE. Here, the radiating lights 300would be evenly distributed over the area covering ⅔ of the area of thecover plate CP. The horizontal collimated film PHOE may be an opticalelement having a holographic pattern configured to collimate thepropagating light 200 having the expanding angle of ϕ on the horizontalplane corresponding to the width of the cover plate CP.

Further referring to the perspective view shown in the lower portion ofFIG. 4, the horizontal collimating film PHOE may be disposed at a lightcovering part LCO defined at the position being apart with apredetermined distance from the light entering part LIN. In the secondembodiment, the image sensing area SA would be substantially the samewith the light going-out part LOT.

<Third Embodiment>

Hereinafter, referring to FIG. 5, explanation will be given about thethird embodiment of the present disclosure. FIG. 5, with (a) being aside view and (b) being a perspective view, is a drawing illustrating astructure of a flat panel display embedding an optical image sensorincluding a directional optical unit and an optical sensor, according tothe third embodiment of the present disclosure.

In the third embodiment, the whole of the display area AA of the displaypanel DP would be used for the image sensing area SA. The flat paneldisplay embedding an optical image sensor is very similar with thesecond embodiment. The difference is that the horizontal collimatingfilm PHOE is disposed at the opposite end non-display area NA of thecover plated CP facing the light incident film CHOE. Further, theradiating lights 300 are provided as the propagating light 200 goes backto the light incident film CHOE from the horizontal collimated filmPHOE.

The flat panel display embedding an optical image sensor according tothe third embodiment of the present disclosure comprises a directionaloptical substrate SLS, a display panel DP and a light source LS. Thedirectional optical substrate SLS is joined on the upper surface of thedisplay panel DP. The light source LS is disposed under the directionaloptical substrate SLS at one side of the display panel DP.

The directional optical substrate SLS includes a cover plate CP, a lightincident film CHOE, a light radiating film VHOE, a horizontalcollimating film PHOE, a first low refractive layer LR1 and a second lowrefractive layer LR2. The light radiating film VHOE may be disposed ascorresponding to the display area AA of the display panel DP. The lightincident film CHOE is disposed at one side of the non-display area NA ofthe display panel DP, laterally near the light radiating film VHOE. Thehorizontal collimating film PHOE is disposed at the other side of thenon-display area AA, laterally near the light radiating film VHOE. Thelight incident film CHOE and the horizontal collimating film PHOE aredisposed at both end sides of the cover plate CP, respectively, asfacing each other with respect to the light radiating film VHOE.

Specifically, the light incident film CHOE may be disposed at anexterior area out of the non-display area NA of the display panel DP. Inthat instance, the light source LS may be disposed at the outside of thedisplay panel DP as facing the light incident film CHOE.

The light incident film CHOE may convert the incident light 100 to atotal reflecting light 210 and provide it inside of the cover plate CP.The total reflecting light 210 propagates to the horizontal collimatingfilm PHOE, and repeats the total reflection within the cover plate CP.In this processing, the total reflecting light 210 is not converted intothe radiating light 300 by the light radiating film VHOE. That is, it ispreferable that the light radiating film VHOE includes a holographicpattern for transmitting the total reflecting light 210 of the thirdembodiment. Therefore, all of the total reflecting lights 210 transmitthe light radiating film VHOE and are totally reflected by the interfacebetween the light radiating film VHOE and the first low refractive layerLR1.

The horizontal collimating film PHOE converts the total reflectinglights 210 into the propagating lights 200 and sends them inside of thecover plate CP. Accordingly, the propagating lights 200 are sent fromthe horizontal collimating film PHE to the light incident film CHOE. Inthis process, some of the propagating lights 200 would be converted intothe radiating lights 300 and sent inside of the cover plate CP by thelight radiating film VHOE, like in the first and second embodiments.That is, it is preferable that the light radiating film VHOE accordingto the third embodiment includes a holographic pattern converting someof the propagating lights 200 into the radiating lights 300.

The radiating lights 300 is totally reflected at the upper surface ofthe second low refractive layer LR2 (i.e., the interface between thesecond low refractive layer LR2 and the air layer), and transmitsthrough the light radiating film VHOE and the first low refractive layerLR1 disposed under the cover plate CP. Further, the upper substrate ofthe display panel DP is attached under the first low refractive layerLR1. It is preferable that the upper substrate of the display panel DPhas the refractive index of 1.5 like the glasses. Accordingly, theradiating lights 300 is not reflected at the interface between the firstlow refractive layer LR1 and the display panel DP, but transmits intothe display panel DP. That is, the radiating lights 300 go out from thedirectional optical substrate SLS.

The radiating lights 300 provided by the directional optical unitaccording to the third embodiment of the present disclosure is differentfrom those of the first embodiment and the second embodiment. Furtherreferring to FIGS. 6A and 6B, explanation will be given about theprocess for providing the radiating lights 300 horizontally collimatedaccording to the third embodiment, in detail. FIGS. 6A and 6B are crosssectional views illustrating light paths inside of the directionaloptical substrate according to the third embodiment.

The incident light 100 having a predetermined cross sectional area andprovided from the light source LS enters onto the light incident pointIP of the light incident film CHOE. Specifically, the incident light 100enters to a normal direction with respect to the surface of the lightincident point IP. The incident light 100 would be converted into atotal reflecting light 210 by the light incident film CHOE. Here, thetotal reflecting light 210 has an incident angle δ satisfying theinternal total reflection condition inside of the cover plate CP.

Specifically, it is preferable that the incident angle of the totalreflecting light 210 satisfies the condition in which the totalreflecting light 210 is not affected by the light radiating film VHOE atall and transmits it. To do so, it is preferable that the lightradiating film VHOE is an optical element having a holographic patternby which some of the lights having the incident angle θ are convertedinto the radiating lights 300. Further, it is preferable that theincident angle of the total reflecting light 210 is the total reflectionangle δ, which is different from the incident angle θ of the propagatinglight 200. That is, the total reflection angle δ may be larger orsmaller than the incident angle θ, but not equal. Here, for example, thetotal reflection angle δ is larger than the incident angle θ.

In the third embodiment, the light incident film VHOE is preferably atransparent film having a holographic pattern by which the incidentlight 100 is converted to the total reflecting light 210 having thetotal reflection angle δ different from the incident angle θ, andsending the total reflecting light 210 into the cover plate CP. Thetotal reflecting light 210 would be propagating from the light incidentfilm CHOE to the horizontal collimating film PHOE along the length axis,i.e., the X-axis.

The total reflecting light 210 would be converted to the propagatinglight 200 by the horizontal collimating film PHOE. The propagating light200 may have very similar optical properties as the propagating light200 explained in the first and the second embodiments. One difference isthat the propagating direction is opposite. For example, the propagatinglight 200 of the third embodiment goes from the horizontal collimatingfilm PHOE to the light incident film CHOE.

In FIG. 6B, the horizontal collimating film PHOE is disposed under thebottom surface of the cover plate CP as being near to the lightradiating film VHOE. However, it is not restricted to this structure. Insome instances, the horizontal collimating film PHOE may be disposed onthe top surface of the cover plate CP (in detail, between the coverplate CP and the second low refractive layer LR2). Alternatively, two ofthe horizontal collimating films PHOE may be disposed on the cover plateCP, on the top surface and under the bottom surface of the cover plateCP, respectively, with the two horizontal collimating films PHOE facingeach other.

The propagating light 200 would be totally reflected at the interfacebetween the cover plate CP and the second low refractive layer LR2, andthen converted to the radiating light 300 by the light radiating filmVHOE. Here, the radiating light 300 may have very similar opticalproperties with those of the first and the second embodiments. Adifference is that the propagating direction may be opposite.

In summary, the incident light 100 is converted to the total reflectinglight 210 having the total reflection angle δ by the light incident filmCHOE. The total reflecting light 210 propagates from the light incidentfilm CHOE to the horizontal collimating film PHOE, repeating theinternal total reflections within the cover plate CP. By the horizontalcollimating film PHOE, the total reflecting light 210 would be convertedto the propagating light 200 having the incident angle θ. Thepropagating light 200 goes from the horizontal collimating film PHOE tothe light incident film CHOE, repeating the internal total reflectionswithin the cover plate CP. By the light radiating film VHOE, some of thepropagating light 200 would be converted to the radiating light 300having the reflection angle α. Other portions of the propagating light200 would be totally reflected at the interface between the lightradiating film VHOE and the first low refractive layer LR1 to the topsurface of the cover plate CP.

It is preferable that the incident angle θ of the propagating light 200is larger than the internal total reflection critical angle T_(VHOE_LR1)at the interface between the light radiating film VHOE and the first lowrefractive layer LR1, and larger than the internal total reflectioncritical angle T_(CP_LR2) at the interface between the cover plate CPand the second low refractive layer LR2. Further, it is preferable thatthe total reflection angle δ of the total reflecting light 210 is largerthan the incident angle θ of the propagating light 200. For example,when the cover plate CP and the light radiating film VHOE have therefractive index of 1.5, and the first low refractive layer LR1 and thesecond low refractive layer LR2 have the refractive index of 1.4, theinternal total reflection critical angle T_(VHOE_LR1) at the interfacebetween the light radiating film VHOE and the first low refractive layerLR1 and the internal total reflection critical angle T_(CP_LR2) at theinterface between the cover plate Cp and the second low refractive layerLR2 would be about 69°. Therefore, it is preferable that the incidentangle θ of the propagating light 200 is larger than 69°.

For example, it is preferable that the incident angle θ may be in arange of 70° to 75°, inclusive. Further, it is preferable that the totalreflection angle δ may be greater than the incident angle θ. Forexample, the total reflection angle δ may be in a range of 75° to 80°,inclusive. In addition, the reflection angle α of the radiating light300 may be in a range of 45° to 55°, inclusive.

Referring to the perspective view shown at lower portion of FIG. 5,explanation will be given about the image sensing area SA. In the thirdembodiment, the total reflecting light 210 having the expanding angle ϕgoes to the horizontal collimating film PHOE from the incident point IP.When being converted from the total reflecting light 210 to thepropagating light 200 by the horizontal collimating film PHOE, thepropagating light 200 is horizontally collimated with respect to thepropagating direction on the XY plane corresponding to the width of thecover plate CP.

For the flat panel display embedding an optical image sensor accordingto the third embodiment of the present disclosure, the whole area of thelight radiating film VHOE disposed between the light incident film CHOEand the horizontal collimating film PHOE is corresponding to the imagesensing area SA. Specifically, the light radiating film VHOE may bedisposed as aligned with and overlapping the display area AA of thedisplay panel DP. In this instance, the whole area of the display areaAA would be used for the image sensing area SA.

In order that the directional optical substrate SLS provides thedirectional sensing lights 400 as covering whole surface of the displaypanel DP, it is preferable that the propagating light 200 is configuredto propagate as satisfying the internal total reflection conditioninside of the cover plate CP. The directional optical substrate SLS isattached on the top surface of the display panel DP. Therefore, it ispreferable that the first low refractive layer LR1 and the second lowrefractive layer LR2 are disposed at the lowermost layer and at theuppermost layer, respectively. When these two low refractive layers LR1and LR2 are omitted, the propagating light 200 is not propagated byrepeating the total reflection process inside of the cover plate CP.Here, the term of ‘low’ in the low refractive layer LR is used forrepresenting the condition in which it has lower refractive index thanthe refractive index of the cover plate CP and the display panel DP.

<Fourth Embodiment>

Until now, we have explained the directional optical unit focusing onthe directional optical substrate SLS. Hereinafter, explanation will begiven about the configurations of the light source LS, in detail. FIGS.7A and 7B are cross sectional views illustrating how the lights areprovided in view of the relationship of the cover plate and the lightsource in the direction optical unit according to the fourth embodiment.Hereinafter drawings are enlarged drawings for showing the light paths.For convenience, the light radiating film VHOE, the light incident filmCHOE, the first low refractive layer LR1 and the second low refractivelayer LR2 are not shown. However, referring to above mentioned drawings,the total structure will be readily understood, including the lightradiating film VHOE, the light incident film CHOE, the first lowrefractive layer LR1 and the second low refractive layer LR2.

Referring to FIG. 7A, the cover plate CP may be a transparent glasssubstrate having thickness of about 0.5 mm. The light source LS mayprovide an infrared laser beam of which cross section is a circle having0.5 mm diameter. FIG. 7A is a cross sectional view illustrating the areafor providing the radiating light when the cover plate is 0.5 mmthickness. In that instance, the incident light 100 is converted to thepropagating light 200 having the incident angle of 70° and sent into thecover plate CP.

The propagating light 200 repeats the total reflection processing withinthe cover plate CP. Accordingly, the propagating lights 200 hitting thelight radiating film are not continuously distributed but are discretelydistributed. For the instance of the 70° incident angle, as shown inFIG. 7A, there is a distance of 2.24 mm between the first hit area (orradiating area) of the propagating light 200 and the second hit area ofthe propagating light 200 to the light radiating film. As the diameterof the incident light 100 is 0.5 mm, there is a distance of 2.24 mmbetween each of the hit area of 0.5 mm diameter. That is, the radiatinglights 300 are provided at the 0.5 mm hit areas arrayed with 2.24 mmdistance (or gap).

Under the same condition, the distance (or gap) of the hit areas may bevaried according to the thickness of the cover plate CP. For example,the cover plate CP may have the thickness of 0.3 mm. FIG. 7B is a crosssectional view illustrating the area for providing the radiating lightwhen the cover plate is 0.3 mm thickness. For the instance of the 70°incident angle, as shown in FIG. 7B, there is a distance of 1.14 mmbetween the first hit area of the propagating light 200 and the secondhit area of the propagating light 200 to the light radiating film. Asthe diameter of the incident light 100 is 0.5 mm, there is a distance of1.14 mm between each of the hit area of 0.5 mm diameter. That is, theradiating lights 300 are provided at the 0.5 mm hit areas arrayed with1.14 mm distance (or gap).

<Fifth Embodiment>

Now, explanation will be given about the structure for enhancing theimage sensing resolution by reducing the distance between each hit areasgenerating the radiating lights 300. In the fifth embodiment, astructure is provided in which two light sources are disposed to reducethe distance or gap between each hit areas providing the radiatinglights. FIG. 8 is a cross sectional view illustrating profiles of thelights inside of the directional optical unit according to the fifthembodiment.

Referring to FIG. 8, the directional optical unit according to the fifthembodiment of the present disclosure comprises a directional opticalsubstrate SLS and two light sources LS1 and LS2. The directional opticalsubstrate SLS may include a cover plate CP, a light radiating film VHOE,a light incident film CHOE, a first low refractive layer LR1 and asecond low refractive layer LR2. The cover plate CP may be a transparentglass substrate of which thickness is 0.3 mm.

The first light source LS1 and the second light source LS2 are disposedas facing the light incident film CHOE, and as being neighbored alongthe X axis, the length direction of the cover plate CP. Specifically,the first and the second light sources LS1 and LS2 may provide theinfrared laser beam having 0.5 mm diameter circle shapes, respectively.The light sources LS1 and LS2 may be spaced apart from each other bydistance of 0.32 mm.

When the incident angle is 70°, as shown in FIG. 8, there is a distanceof 1.14 mm between the first hit area and the second hit area of thepropagating light 200 from the first light source LS1. In addition,there is also a distance of 1.14 mm between the first hit area and thesecond hit area of the propagating light 200 from the second lightsource LS2.

Accordingly, there is 0.32 mm gap between each hit area of thepropagating light 200 having 0.5 mm diameter. That is, the radiatinglights 300 may be provided from the 0.5 mm hit areas arrayed with thegap of 0.32 mm.

<Sixth Embodiment>

In the sixth embodiment, a structure is provided for reducing the gapbetween neighboring hit areas providing the radiating lights using alight source generating the incident light 100 having an asymmetriccross sectional shape. FIG. 9 is a cross sectional view illustratingprofiles of the lights inside of the directional optical unit accordingto the sixth embodiment.

Referring to FIG. 9, the directional optical unit according to the sixthembodiment of the present disclosure comprises a directional opticalsubstrate SLS and a light source LS. The directional optical substrateSLS includes a cover plated CP, a light radiating film VHOE, a lightincident film CHOE, a first low refractive layer LR1 and a second lowrefractive layer LR2. The cover plate CP may be a transparent glasssubstrate of which thickness is 0.3 mm.

The light source LS may generate an infrared laser beam of which crosssectional area is an asymmetric shape, such as an ellipse. For example,the ellipse shapes of the laser beam provided from the light source LSmay have a first axis and a second axis, perpendicular each other. Inone or more embodiments, the length ratio of the first axis and thesecond axis may be in range of 1:2 to 1:4, inclusive. Further, the firstaxis may be disposed along the Y axis, the width direction of the coverplate CP and the second axis may be disposed along the X axis, thelength direction of the cover plate CP. For example the cross sectionalshape of the incident light 100 provided from the light source may be anellipse in which the length axis is 1.0 mm and the width axis is 0.5 mm.

When the incident angle is 70°, as shown in FIG. 9, there is a distanceof 0.64 mm between the first hit area and the second hit area of thepropagating light 200 from the light source LS to the light radiatingfilm VHOE.

The asymmetric cross sectional shape of the incident light 100 may have1.0 mm along the length direction. Between each of hit areas having 1.0mm cross sectional area, there is a 0.64 mm gap. That is, the radiatinglights 300 are provided at the hit areas having 1.0 mm length arrayedwith 0.64 mm gap.

Even though it is not shown, for another example, the cross sectionalshape of the incident light 100 provided from the light source LS mayhave an ellipse in which length axis is 1.5 mm and the width axis is 0.5mm. When the incident angle is 70°, the radiating lights 300 areprovided at the hit areas having 1.5 mm length arrayed with 0.14 mm gap.

Even though it is not shown, for still another example, the crosssectional shape of the incident light 100 provided from the light sourceLS may have an ellipse in which length axis is 2.0 mm and the width axisis 0.5 mm. When the incident angle is 70°, the radiating lights 300 areprovided at the hit areas overlapped each other. Therefore, there is nogap between the hit areas of the propagating lights 200. Accordingly,the radiating lights 300 may be covering over all area of the lightradiating film. At the overlapped areas, the light brightness orintensity may be stronger than non-overlapped areas, but it does notcause any problems for detecting the image.

<First Application Example>

Until now, we explained the features of the present disclosure based onthe directional optical unit for providing the directional lights in theflat panel display embedding an optical image sensor. Hereinafter,explanation will be given about the application embodiment for the wholestructure of the flat panel display embedding an optical image sensorformed by joining the flat panel display with a directional optical unitaccording to embodiments of the present disclosure.

Referring to FIG. 10, explanation will be given about a flat paneldisplay embedding an optical image sensor according to the firstapplication example. FIG. 10 is a cross sectional view illustrating astructure of a liquid crystal display embedding an optical image sensorincluding a directional optical unit and an optical sensor according tothe first application example.

The liquid crystal display embedding an optical image sensor accordingto the first application example comprises a liquid crystal displaypanel LCP, a directional optical substrate SLS and a light source LS.The liquid crystal display panel LCP includes a lower substrate SL andan upper substrate SU joining each other and a liquid crystal layer LCdisposed between the two substrates SL and SU. On the lower substrateSL, a plurality of the pixel areas are disposed in a matrix manner. Atthe upper substrate SU, a plurality of color filters is disposed as eachcolor filter is corresponding to each pixel area. Otherwise, the uppersubstrate SU may have any additional elements as may be known. Here, theliquid crystal display panel LCP shown in FIG. 10 is one of a horizontalelectric field type. However, embodiments provided herein are notrestricted to this type of liquid crystal display panel, but varioustype liquid crystal display panels may be used.

Within each pixel area, the pixel electrode PXL and the common electrodeCOM are disposed for representing video images. Further, the thin filmtransistor T would be disposed for selectively supplying the videosignal to the pixel electrode PXL. The photo sensor TS may be disposednear the thin film transistor T. At least one photo sensor TS may bedisposed at each of the pixel areas. In one or more embodiments, onephoto sensor TS may be disposed at a corresponding set of the pixelareas.

On the top surface of the upper substrate SU of the liquid crystaldisplay panel LCP, the directional optical substrate SLS according tothe embodiments of the present disclosure is attached in a face-to-facemanner. The directional optical substrate SLS includes a cover plate CP,a light incident film CHOE, a light radiating film VHOE, a first lowrefractive layer LR1 and a second low refractive layer LR2. The firstlow refractive layer LR1 of the directional optical substrate SLS isattached with the top surface of the upper substrate SU.

The liquid crystal display panel LCP is one of the non-self emissiondisplay panel which cannot radiate the light. Therefore, a back lightunit BLU may be required under the bottom surface of the lower substrateSL. At one lateral side, the light source LS may be disposed as facingthe light incident film CHOE. The light source LS may be configured withthe back light unit BLU as the one-body system. Otherwise, the lightsource LS may be disposed near the back light unit BLU as being apartfrom the back light unit BLU.

The liquid crystal display panel LCP includes a display area AA and anon-display area NA. The light radiating film VHOE of the directionaloptical substrate SLS may be disposed as corresponding to the displayarea AA. The light source LS may be disposed in the non-display area NAas facing the light incident film CHOE.

<Second Application Example>

Referring to FIG. 11, explanation will be given about a flat paneldisplay embedding an optical image sensor according to the secondapplication example. FIG. 11 is a cross sectional view illustrating astructure of an organic light emitting diode display embedding anoptical image sensor including a directional optical unit and an opticalsensor according to the second application example.

The organic light emitting diode display embedding an optical imagesensor according to the second application example comprises an organiclight emitting diode display panel OLP, a directional optical substrateSLS and a light source LS. The organic light emitting diode displaypanel OLP includes a substrate SUB having the display elements and anen-cap ENC, as attaching each other in a face-to-face manner. On thesubstrate SUB, a plurality of pixel areas is disposed in a matrixmanner. At the en-cap ENC, a plurality of color filters may be disposedas each color filter is corresponding to each pixel area. Otherwise, theen-cap ENC may be a transparent substrate without any specific elements.Here, the organic light emitting diode display panel OLP shown in figureis one of the top emission type. However, embodiments provided hereinare not restricted to the top emission type, but various types includingbottom emission type or both side emission type may be used.

Within each pixel area, the organic light emitting diode OLE forrepresenting the video image and the thin film transistor T forselectively supplying the video data to the organic light emitting diodeOLE are disposed. The organic light emitting diode OLE includes an anodeelectrode ANO, an organic light emitting layer OL and a cathodeelectrode CAT. The photo sensor TS may be disposed near the thin filmtransistor T. At least one photo sensor TS may be disposed at each ofthe pixel area. Otherwise, one photo sensor TS may be disposed at a setof the pixel areas.

On the top surface of the en-cap ENC of the organic light emitting diodedisplay panel OLP, the directional optical substrate SLS according tothe embodiments of the present disclosure is attached in a face-to-facemanner. The directional optical substrate SLS includes a cover plate CP,a light incident film CHOE, a light radiating film VHOE, a first lowrefractive layer LR1 and a second low refractive layer LR2. The firstlow refractive layer LR1 of the directional optical substrate SLS isattached with the top surface of the en-cap ENC.

The organic light emitting diode display panel OLP is one of theself-emission display panel type which can radiate the light. Therefore,it does not require the back light unit BLU. Therefore, it is preferablethat the light source LS is disposed at one lateral side of the organiclight emitting diode display OLP as facing the light incident film CHOE.

In detail, the organic light emitting diode display panel OLP includes adisplay area AA and a non-display area NA. It is preferable that thedirectional optical substrate SLS has slightly larger size than theorganic light emitting diode display panel OLP. The light radiating filmVHOE of the directional optical substrate SLS may be disposed ascorresponding to the display area AA. The light incident film CHOE maybe disposed as covering an exterior space extended from one lateral sideof the organic light emitting diode display panel OLP. The light sourceLS may be disposed under the exterior space as facing the light incidentfilm CHOE.

As mentioned above, the display embedding an optical image sensorincludes a cover plate disposed at the outermost surface and an ultrathin film type holographic film having at most some hundreds of μm ofthickness and attached at one side of the cover plate. Therefore, theoptical image sensor according to the present disclosure can beconfigured with the display panel in which the total thickness is notmuch thicker. Further, evenly distributing the highly collimated sensinglights over the most surface of the display panel, the ultra highresolution for image sensing would be acquired. Therefore, it is veryefficient to detect tiny image pattern such as fingerprint or palm printon the large area, exactly or more accurately.

<Third Application Example>

Referring to FIG. 12, explanation will be given about a flat paneldisplay embedding an optical image sensor according to the thirdapplication example. FIG. 12 is a cross sectional view illustrating astructure of an organic light emitting diode display embedding anoptical image sensor including a directional optical unit and an opticalsensor according to the third application example.

In this third application example, we explain about another structurefor applying the directional optical unit of the present disclosure withthe flat panel display. In the above explained embodiments and examples,the directional optical unit is configured by using the cover plate CPof the flat panel display. The third application example suggests astructure in which the directional optical unit is separated from thecover plate.

The organic light emitting diode display embedding an optical imagesensor according to the third application example comprises an organiclight emitting diode display panel OLP, a directional optical substrateSLS and a light source LS. The organic light emitting diode displaypanel OLP includes a substrate SUB having the display elements and anen-cap ENC for protecting the display elements, as attaching each otherin a face-to-face manner. On the substrate SUB, a plurality of pixelareas is disposed in a matrix manner. The organic light emitting diodedisplay panel OLP may have a plurality of color filters corresponding toeach pixel areas. The en-cap ENC may include a single layer or multiplelayers of the organic layer and/or the inorganic layer. Here, theorganic light emitting diode display panel OLP shown in the figure isone of the top emission type. However, embodiments provided herein arenot restricted to the top emission type, but various types includingbottom emission type or both side emission type may be used.

Within each pixel area, the organic light emitting diode OLE forrepresenting the video image and the thin film transistor T forselectively supplying the video data to the organic light emitting diodeOLE are disposed. The organic light emitting diode OLE includes an anodeelectrode ANO, an organic light emitting layer OL and a cathodeelectrode CAT. The photo sensor TS may be disposed near the thin filmtransistor T. At least one photo sensor TS may be disposed at each ofthe pixel areas. Otherwise, one photo sensor TS may be disposed at a setof the pixel areas.

On the top surface of the en-cap ENC of the organic light emitting diodedisplay panel OLP, the directional optical substrate SLS according tothe embodiments of the present disclosure is attached in a face-to-facemanner. Here, the directional optical substrate SLS includes a lightguide optical plate LGP different from the cover plate CP. Further, acover plate CP for protecting the display elements is attached on theupper surface of the directional optical substrate SLS.

The directional optical substrate SLS includes a light guide opticalplate LGP working as the light guide, a light incident film CHOE, alight radiating film VHOE, a first low refractive layer LR1 and a secondlow refractive layer LR2. The first low refractive layer LR1 of thedirectional optical substrate SLS is attached with the top surface ofthe en-cap ENC.

It is preferable that the light guide optical plate LGP includes atransparent thin substrate or a transparent film having the refractiveindex of 1.5 the same with that of the cover plate CP. For example, thelight guide optical plate LGP may include the poly carbonate, thepolymethyl methacrylate, the glass material and so on. The lightradiating film VHOE and the light incident film CHOE are attached underthe lower surface of the light guide optical plate LGP. It is preferablethat the light guide optical plate LGP, the light radiating film VHOEand the light incident film CHOE have the refractive index of 1.5.

It is preferable that the light guide optical plate LGP, the lightradiating film VHOE and the light incident film CHOE are insertedbetween the first low refractive layer LR1 and the second low refractivelayer LR2. It is preferable that the first low refractive layer LR1 andthe second low refractive layer LR2 may be a transparent film or atransparent layer having the refractive index of 1.4. That is, the stackstructure is such that two stacked higher refractive layers (refractiveindex=1.5) are inserted between the two lower refractive layers(refractive index=1.4). Therefore, this stack structure satisfies thecondition in which the lights propagates from one side to the oppositeside without loss by the total reflection between the first lowrefractive layer LR1 and the second low refractive layer LR2.

It is preferable that the light incident film CHOE has a holographicpattern that converts the incident lights into the propagating lights.The incident lights vertically enter into the light incident film CHOE.The propagating lights have the incident angle for satisfying the totalreflection condition between the first low refractive layer LR1 and thesecond low refractive layer LR2. Further, it is preferable that thelight radiating film VHOE has a holographic pattern that coverts some ofthe propagating lights to have another incident angle to break the totalreflection condition so that some of the propagating lights enter intothe first low refractive layer LR1 and the second low refractive layerLR2, but the others of the propagating lights maintain the incidentangle for satisfying the total reflection condition between the firstlow refractive layer LR1 and the second low refractive layer LR2.

The organic light emitting diode display panel OLP is one of theself-emission display panel type which can radiate the light. Therefore,it does not require the back light unit BLU. Therefore, it is preferablethat the light source LS is disposed at one lateral side of the organiclight emitting diode display OLP as facing the light incident film CHOE.

In detail, the organic light emitting diode display panel OLP includes adisplay area AA and a non-display area NA. It is preferable that thedirectional optical substrate SLS has slightly larger size than theorganic light emitting diode display panel OLP. The light radiating filmVHOE of the directional optical substrate SLS may be disposed ascorresponding to the display area AA. The light incident film CHOE maybe disposed as covering an exterior space extended from one lateral sideof the organic light emitting diode display panel OLP. The light sourceLS may be disposed under the exterior space as facing the light incidentfilm CHOE.

In the third application example, the directional optical unit SLS maybe manufactured individually unlike that the first and the secondapplication examples in which the directional optical unit SLS ismanufactured by using the cover plate as the light guide plate. Thedirectional optical unit SLS of the third application example isdisposed between the cover plate CP and the display panel. The coverplate CP is attached on the upper surface of the second low refractivelayer LR2 of the directional optical unit SLS.

The directional optical unit SLS according to the third applicationexample has the similar structures of the first and the secondapplication examples, excepting that the cover plate CP is used for thelight guide optical plate. By applying the cover plate CP as the lightguide optical plate LGP of the third application example, it may be theorganic light emitting diode display embedding an optical image sensorincluding a directional optical unit and an optical sensor according tothe second application example.

While the embodiments of the present disclosure have been described indetail with reference to the drawings, it will be understood by thoseskilled in the art that the disclosure can be implemented in otherspecific forms without changing the technical spirit or essentialfeatures of the disclosure. Therefore, it should be noted that theforgoing embodiments are merely illustrative and are not to be construedas limiting the disclosure. The scope of the disclosure is defined bythe appended claims rather than the detailed description of thedisclosure. All changes or modifications or their equivalents madewithin the meanings and scope of the claims should be construed asfalling within the scope of the disclosure.

What is claimed is:
 1. A flat panel display device embedding an imagesensor, the device comprising: a display panel including a display areaand a non-display area, and having a top surface; and a directionaloptical unit attached to the top surface of the display panel, thedirectional optical unit having a length along a length axis of thedisplay panel, a width along a width axis of the display panel and athickness along a thickness axis of the display panel, wherein thedirectional optical unit provides a propagating light in the displayarea, wherein the propagating light is collimated and directionizedalong a predetermined direction of the directional optical unit, andwherein some of the propagating light is converted into a radiatinglight using a light radiating film.
 2. The device according to claim 1,wherein the directional optical unit includes: a light guide opticalplate having a size corresponding to the length and the width of thedirectional optical unit; the light radiating film corresponding to thedisplay area, the light radiating film positioned under the light guideoptical plate; a light incident film positioned under the light guideoptical plate and disposed outside of the display area adjacent to alateral side of the light radiating film; a first low refractive layerdisposed under the light radiating film and the light incident film, thefirst low refractive layer attached on the top surface of the displaypanel, and having a first refractive index that is lower than that ofthe light guide optical plate and that of the light radiating film; asecond low refractive layer disposed on the light guide optical plate,and having a second refractive index lower than that of the light guideoptical plate; and a light source positioned under the light incidentfilm.
 3. The device according to claim 2, wherein the light sourceprovides an incident light to an incident point on a surface of thelight incident film; wherein the light incident film includes a firstholographic pattern that converts the incident light to a propagatinglight having an incident angle satisfying an internal total reflectioncondition of the light guide optical plate, and that transmits thepropagating light into the light guide optical plate; and wherein thelight radiating film includes a second holographic pattern that convertsa portion of the propagating light into the sensing light, the sensinglight having a reflection angle that satisfies a total reflectioncondition at a top surface of the second low refractive layer and thatsatisfies a transmitting condition through the first low refractivelayer and the display panel.
 4. The device according to claim 3, whereinthe propagating light has an expanding angle on a horizontal planeincluding the length axis and the width axis of the display panel, andthe propagating light maintains a collimated state on a vertical planeincluding the length axis and the thickness axis of the display panel;wherein the incident angle is larger than a first internal totalreflection critical angle at a first interface between the lightradiating film and the first low refractive layer, and larger than asecond internal total reflection critical angle at a second interfacebetween the light guide optical plate and the second low refractivelayer; and wherein the reflection angle is larger than a third totalreflection critical angle at a third interface between the second lowrefractive layer and an air layer, and smaller than a fourth totalreflection critical angle at a fourth interface between the first lowrefractive layer and the display panel.
 5. The device according to claim4, wherein the expanding angle is equal to or greater than an innerangle between a first line and a second line, the first line is astraight line between the incident point and a first end of a side ofthe light guide optical plate opposite to the light incident film, andthe second line is a straight line between the incident point and asecond end of the side of the light guide optical plate opposite to thelight incident film.
 6. The device according to claim 4, wherein thedirectional optical unit further includes: a horizontal collimating filmdisposed under the light guide optical plate between the light incidentfilm and the light radiating film, the horizontal collimating filmhaving a width corresponding to the width of the directional opticalunit, wherein the expanding angle is equal to or greater than an innerangle between a first line and a second line, the first line is astraight line between the incident point and a first end of a side ofthe horizontal collimating film opposite to the light incident film, andthe second line is a straight line between the incident point and asecond end of the side of the horizontal collimating film opposite tothe light incident film, and wherein the horizontal collimating filmincludes a third holographic pattern that horizontally collimates thepropagating light having the expanding angle on the horizontal planecorresponding to the width of the directional optical unit.
 7. Thedevice according to claim 4, wherein the directional optical unitfurther includes: a horizontal collimating film disposed at an oppositeside of the light guide optical plate facing the light incident film inthe non-display area, wherein the light incident film includes a thirdholographic pattern that converts the incident light to a totalreflecting light having a total reflection angle different from theincident angle, and that transmits the total reflecting light into thelight guide optical plate, wherein the expanding angle is equal to orgreater than an inner angle between a first line and a second line, thefirst line is a straight line between the incident point and a first endof a side of the horizontal collimating film, and the second line is astraight line between the incident point and a second end of the side ofthe horizontal collimating film, the second end being opposite to thefirst end, wherein the horizontal collimating film includes a thirdholographic pattern that horizontally collimates the propagating lighthaving the expanding angle on the horizontal plane corresponding to thewidth, and that converts the total reflecting light to the propagatinglight and transmits the propagating light to the light incident film,and wherein the second holographic pattern of the light radiating filmis for transmitting the total reflecting light therethrough.
 8. Thedevice according to claim 7, wherein the horizontal collimating film isdisposed on at least one of a bottom surface and an upper surface of thelight guide optical plate.
 9. The device according to claim 2, whereinthe light source provides a collimated light having a circularcross-sectional shape.
 10. The device according to claim 9, wherein thelight source includes at least two unit light sources disposed with apredetermined distance between them.
 11. The device according to claim9, wherein the light source includes a cross-sectional shape of anellipse having a first axis corresponding to a width direction of thelight source and a second axis corresponding to a length direction ofthe light source, wherein a ratio of a first dimension of the ellipsealong the first axis to a second dimension of the ellipse along thesecond axis is within a range of 1:2, inclusive, to 1:4, inclusive. 12.The device according to claim 2, wherein the light guide optical plateis a cover plate of the display panel.
 13. The device according to claim2, further including: a cover plate attached on the first low refractivelayer.
 14. The device according to claim 13, wherein the cover plate isformed of a transparent reinforced glass.
 15. A flat panel displaydevice embedding an image sensor, the device comprising: a display panelincluding a display area and a non-display area; and a directionaloptical unit attached on a surface of the display panel, the directionaloptical unit having a light exiting part and a light entering part thatare adjacent to each other, wherein the directional optical unitinternally reflects a propagating light, converts some of thepropagating light into a radiating light using a light radiating film,converts the radiating light into a sensing light, and provides thesensing light to the display area of the display panel from the lightexiting part.
 16. The device according to claim 15, wherein thedirectional optical unit includes: a light guide optical plate having asize corresponding to a length and a width of the directional opticalunit; the light radiating film corresponding to the display area, thelight radiating film positioned under the light guide optical plate; alight incident film positioned under the light guide optical plate anddisposed outside of the display area adjacent to a lateral side of thelight radiating film; a first low refractive layer disposed under thelight radiating film and the light incident film, the first lowrefractive layer attached on the display panel, and having a firstrefractive index that is lower than that of the light guide opticalplate and that of the light radiating film; a second low refractivelayer disposed on the light guide optical plate, and having a secondrefractive index lower than that of the light guide optical plate; and alight source positioned under the light incident film.
 17. The deviceaccording to claim 16, wherein the light source provides an incidentlight to an incident point on a surface of the light incident film;wherein the light incident film includes a first holographic patternthat converts the incident light to the propagating light having anincident angle satisfying an internal total reflection condition of thelight guide optical plate, and that transmits the propagating light intothe light guide optical plate; and wherein the light radiating filmincludes a second holographic pattern that converts a portion of thepropagating light into the sensing light, the sensing light having areflection angle that satisfies a total reflection condition at a topsurface of the second low refractive layer and that satisfies atransmitting condition through the first low refractive layer and thedisplay panel.
 18. The device according to claim 17, wherein thepropagating light has an expanding angle on a horizontal plane includinga length axis and a width axis of the display panel, and the propagatinglight maintains a collimated state on a vertical plane including thelength axis and a thickness axis of the display panel; wherein theincident angle is larger than a first internal total reflection criticalangle at a first interface between the light radiating film and thefirst low refractive layer, and larger than a second internal totalreflection critical angle at a second interface between the light guideoptical plate and the second low refractive layer; and wherein thereflection angle is larger than a third total reflection critical angleat a third interface between the second low refractive layer and an airlayer, and smaller than a fourth total reflection critical angle at afourth interface between the first low refractive layer and the displaypanel.
 19. The device according to claim 18, wherein the expanding angleis equal to or greater than an inner angle between a first line and asecond line, the first line is a straight line between the incidentpoint and a first end of a side of the light guide optical plateopposite to the light incident film, and the second line is a straightline between the incident point and a second end of the side of thelight guide optical plate opposite to the light incident film.
 20. Thedevice according to claim 19, wherein the directional optical unitfurther includes: a horizontal collimating film disposed under the lightguide optical plate between the light incident film and the lightradiating film, the horizontal collimating film having a widthcorresponding to the width of the directional optical unit, wherein theexpanding angle is equal to or greater than an inner angle between afirst line and a second line, the first line is a straight line betweenthe incident point and a first end of a side of the horizontalcollimating film opposite to the light incident film, and the secondline is a straight line between the incident point and a second end ofthe side of the horizontal collimating film opposite to the lightincident film, and wherein the horizontal collimating film includes athird holographic pattern that horizontally collimates the propagatinglight having the expanding angle on the horizontal plane correspondingto the width of the directional optical unit.